Crashed 737 Max jets lacked safety features Boeing sold as extras
- 5 years ago
CHICAGO — The doomed 737 Max jets in Indonesia and Ethiopia were not equipped with two notable safety features because Boeing charged an additional cost to install them.
According to the New York Times, the MCAS software on the Boeing 737 Max takes readings from one of two angle of attack sensors on the plane that aligns itself with oncoming airflow.
If MCAS detects that the plane is pointed up at a dangerous angle, it automatically swivels the horizontal stabilizer and pushes the nose down to prevent stalling.
Two optional safety features could have kept the MCAS in check: the angle of attack indicator displays readings from both sensors, and the disagree light activates when the sensors' data do not match.
Both features were sold by Boeing as optional extras and were not included on the crashed Lion Air and Ethiopian Airlines planes.
According to the New York Times, the safety features could have helped pilots detect any erroneous readings. This would have also allowed a manual override of the system.
The Times, citing a Boeing bulletin, says this can be done by temporarily counteracting the MCAS movement, cutting off electrical power to the stabilizers, and then cranking a wheel to manually pull them back to the correct position.
Experts told the newspaper that the two features are vital for flight safety. But because neither is mandated by the FAA, Boeing was able to sell them as upgrades.
The company has since announced that it will make the disagree light standard on all new 737 aircrafts, but the angle of attack indicator will remain an optional extra that airlines can buy.
According to the New York Times, the MCAS software on the Boeing 737 Max takes readings from one of two angle of attack sensors on the plane that aligns itself with oncoming airflow.
If MCAS detects that the plane is pointed up at a dangerous angle, it automatically swivels the horizontal stabilizer and pushes the nose down to prevent stalling.
Two optional safety features could have kept the MCAS in check: the angle of attack indicator displays readings from both sensors, and the disagree light activates when the sensors' data do not match.
Both features were sold by Boeing as optional extras and were not included on the crashed Lion Air and Ethiopian Airlines planes.
According to the New York Times, the safety features could have helped pilots detect any erroneous readings. This would have also allowed a manual override of the system.
The Times, citing a Boeing bulletin, says this can be done by temporarily counteracting the MCAS movement, cutting off electrical power to the stabilizers, and then cranking a wheel to manually pull them back to the correct position.
Experts told the newspaper that the two features are vital for flight safety. But because neither is mandated by the FAA, Boeing was able to sell them as upgrades.
The company has since announced that it will make the disagree light standard on all new 737 aircrafts, but the angle of attack indicator will remain an optional extra that airlines can buy.